ATM has been selected as a world standard for broadband ISDN in network communication systems. ATM systems have been implemented on a global basis and developed in a rapid growth. ATM technology is destined to play a major role in both public and private broadband networks. AAL2 is one of the four types of AAL (ATM Adaptive Layer) protocols which have been recommended by CCITT (now ITU-T), namely AAL1, AAL2, AAL3/4 and AAL5. In general, the layer services provided by AAL1 are constant bit rate (CBR) services, which require information to be transferred between source and destination at a constant bit rate. AAL2 offers a transfer of information with a variable bit rate. In addition, timing information is transferred between source and destination. Since the source is generating a variable bit rate, it is possible that cells are not completely filled and that filling level varies from cell to cell. AAL3/4 is used for transfer of data, which is sensitive to loss, but not sensitive to delay. The AAL3/4 protocol may be used for connection oriented as well as for connectionless data communication. AAL3/4 itself does not perform all functions required by a connectionless service, since functions like routing and network addressing are performed on the network layer. AAL5 is designed to offer a service with less overhead and better error detection below the common part of the convergence sublayer (CPCS).
The AAL2 signaling protocol describes methods by which a switched AAL2 connection can be established between two AAL2 end users across a network that consists of both ATM and AAL2 switches. The important function of AAL2 signaling protocol is to establish an AAL2 connection between two AAL2 end points on a concatenation of ATM Virtual Channel Connections (VCCs) that are either on-demand virtual circuit (SVC—switched virtual circuit) or semi-permanent virtual circuit (PVC—permanent virtual circuit). Some the basic requirements of AAL2 signaling protocol include the ability to establish an AAL2 connection between AAL2 end systems that support AESA (ATM End System Address) formats, the ability to support hop-by-hop routing mechanism between AAL2 end systems, the ability to indicate any failures to corresponding management entity, and the ability to setup AAL2 connections with different QoS requirements.
In AAL2, packets (minicells) from many users are assembled into a single ATM cell and transmitted on the same ATM connection. In addition, packets are allowed to straddle across ATM cell boundary to maximize the bandwidth utilization.
Historically, the control signaling, for the setup of an AAL2 point-to-point connection for the establishment of a new call, all terminated at a single media gateway. In prior art media gateways it is not possible to individually terminate the bearer control signaling without having individual signaling facilities on each gateway. Each media gateway must have its own broadband SS7 signaling gateway used only for that media gateway. Only the resources of a single media gateway are available for a particular call.
Thus, there is a need for systems with greater signaling capacity and efficiency than is currently available in the field of media gateways.